JP2003280041A - Light deflecting element, light deflector, and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light deflecting element having simple configuration, a small size, quick responsiveness suitable for a pixel shift element and a deflection quantity stable to the change of temperature. <P>SOLUTION: The light deflecting element has a pair of transparent substrates 2 and 3 opposed to each other at a prescribed interval by using a spacer means, a liquid crystal layer 5 held in a layer shape between the substrates and capable of forming a chiral smectic C phase, a vertical alignment layer 4 formed on the surface of at least one substrate 2 on the side in contact with the liquid crystal layer 5 and one or more pairs of electrodes 6 disposed so that an electric field can be applied to the liquid crystal layer in the direction nearly orthogonal to the layer thickness direction and the liquid crystal layer 5 is constituted of a liquid crystal material which does not form a smectic A phase at the temperature higher than the temperature at which the chiral smectic C phase is formed. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light deflection element / light deflection device and an image display device. INDUSTRIAL APPLICATION This invention can be utilized suitably for electronic display apparatuses, such as a projection display and a head mounted display.

[0002]

2. Description of the Related Art A light deflection element is known as an optical element that deflects an optical path of light by an electric signal from the outside.
That is, the optical axis of the light emitted from the light deflection element can be “shifted in parallel” and / or “rotated at an angle” with respect to the incident light.

As an optical deflecting element, an "optical deflecting element using a liquid crystal" has been proposed and is being implemented as an element that can be realized at a lower cost than the conventionally known "electro-optical device and acousto-optical device". 6-18940 gazette,
JP-A-9-133904).

On the other hand, recently, in a display device such as a projector using an image display element such as a liquid crystal light valve, the optical path of the image light from the image display element is deflected for each of a plurality of subfields obtained by temporally dividing the image field. However, by displaying an image pattern in which the display position is displaced according to the optical path deflection for each subfield, the number of pixels of the image display element is "apparently multiplied" for display. "Pixel shift element" that deflects
As such, an optical deflecting element has come to be used (Japanese Patent No. 2939826 and Japanese Patent Laid-Open No. 5-31311).
6, JP-A-6-324320, JP-A-10
-133135 gazette etc.).

Pixel shift elements are required to "have good responsiveness to high-speed driving", but the "liquid crystal is described in the above-mentioned JP-A-6-18940 and JP-A-9-133904. Since the liquid crystal material used is a nematic liquid crystal or a smectic A phase ferroelectric liquid crystal, it is difficult to realize the sub-millisecond response speed required for the pixel shift element.

As a liquid crystal material having a high response speed, there is a material showing a "chiral smectic C layer", and a light modulation element using the same (JP-A-7-20417) and a high-contrast liquid crystal element (JP-A-7-27). No. 306421) is known.

When a light deflection element using a liquid crystal is used as a pixel shift element of a projector, the element area is relatively large and it is used in a high temperature region due to the influence of heat from a light source. It is necessary to consider how the optical characteristics of the deflecting element change with changes in temperature.

That is, the temperature dependence of the tilt angle of the liquid crystal molecules must be fully taken into consideration.
Japanese Patent Laid-Open No. 17-306421 and Japanese Patent Laid-Open No. 7-306421 do not sufficiently examine the change in optical characteristics due to the temperature dependence of the tilt angle of liquid crystal molecules.

[0009]

SUMMARY OF THE INVENTION In view of the above, the present invention has a simple structure and a small size, has a small light amount loss, optical noise, and a low resolution, is low in cost, and has a high responsiveness suitable for a pixel shift element. It is an object to realize an “optical deflector using liquid crystal” and a “optical deflector” using the same, which has a stable deflection amount against temperature changes.

Another object of the present invention is to realize a novel image display device using the above-mentioned light deflecting device.

[0011]

A light deflection element according to the present invention comprises a pair of transparent substrates, a liquid crystal layer, a vertical alignment film, and 1
It has the above electrode pairs.

The "pair of transparent substrates" are opposed to each other with a predetermined interval by spacer means.

The "liquid crystal layer" is held as a layer between a pair of substrates and is capable of forming a chiral smectic C phase at room temperature. The normal temperature mentioned here refers to a range in which the temperature of the light deflection element fluctuates in a general situation where the light deflection element is used.

The "vertical alignment film" is formed on the surface of at least one of the substrates which is in contact with the liquid crystal layer and vertically aligns the liquid crystal layer.

The "one or more electrode pairs" are arranged so that an electric field can be applied to the liquid crystal layer in a direction substantially orthogonal to the layer thickness direction.

The optical deflector according to claim 1 is characterized by the following points. That is, the liquid crystal layer is composed of "a liquid crystal material that does not form a smectic A phase at a temperature higher than that of the chiral smectic C phase".

Since the temperature dependence of the tilt angle of chiral smectic C phase is small, even if the temperature of the light deflection element changes, the change in the deflection amount of the optical path is small and "a stable deflection amount is obtained regardless of the temperature change". Is possible.

The liquid crystal layer of the optical deflecting element according to the above-mentioned claim 1 has "an end chain portion, a skeleton portion, a spacer portion, and a chiral end portion which are bonded in this order, and at least a part of the skeleton portion has an ester bond. One or more kinds of liquid crystal materials having a molecular structure in which the carbonyl group is bound to the chiral terminal side can be included (claim 2).

With the above materials, a "liquid crystal material that does not form a smectic A phase" can be obtained with certainty, and the temperature dependence of the tilt angle in the chiral smectic C phase becomes small, and "a stable deflection amount regardless of temperature change". Can be surely obtained.

According to another aspect of the optical deflecting element of the present invention, the liquid crystal material of the liquid crystal layer is cooled from the state of the isotropic phase or the chiral nematic phase to form the chiral smectic C phase, at least for a certain period of time in the external phase. To which an electric field has been applied ”(Claim 3).

Thus, by "applying an external electric field at a temperature at which a chiral smectic C phase is formed",
It is possible to prevent the generation of minute domains in which the alignment directions of the liquid crystal molecules are not uniform, improve the uniformity of the alignment direction in the entire liquid crystal layer, and to scatter light at the boundaries of the minute domains and the light between each minute domain. It is possible to prevent a difference in the amount of deflection, prevent light scattering, etc., and perform a uniform light deflection operation.

The optical deflecting device of the present invention uses the optical deflecting element according to claim 1, 2 or 3, and applies a voltage between the electrodes of the electrode pair of the optical deflecting element to apply an electric field to the liquid crystal layer. "Applying means" for changing the average optical axis tilt direction of the liquid crystal layer according to the strength and direction of the applied electric field to deflect the transmission path of linearly polarized light (claim 4).

The optical deflector according to the present invention can have "a polarization direction control means for making the polarization direction of the light incident on the light deflection element coincident with the average inclination direction of the optical axis of the liquid crystal layer" ( Claim 5).

By doing so, even if the incident light is non-polarized light, the light transmitted through the polarization direction control means, that is, the deflection direction of the optical path "the average optical axis of the liquid crystal layer when an electric field is applied Since only light having a polarization direction parallel to the "tilt direction" is incident on the light deflection element, generation of undeflected light is prevented and the contrast of the deflection operation is improved.

According to a sixth aspect of the present invention, there is provided the optical deflector according to the fourth aspect, wherein the two optical deflectors according to the fourth aspect are arranged such that the electric field application directions in the respective optical deflectors are substantially orthogonal to each other, and the optical deflectors are substantially in the light advancing direction. "The polarization direction of the incident light is aligned with the average optical axis inclination direction of the liquid crystal layer of the light deflecting element in the light deflecting device on the light incident side. "Polarization direction control means" is disposed, and "polarization plane rotation means for rotating the polarization plane by 90 degrees" is provided between both light deflectors.

As described above, two optical deflecting elements capable of deflecting in one direction are combined, arranged so that the electric field applying directions of both are rotated by 90 degrees, and the deflecting surface of the light emitted from the incident side optical deflecting element is arranged. Is rotated by 90 degrees and is incident on the second light deflection element, it is possible to reliably perform light deflection in the two-dimensional direction.

The image display device of the present invention has an image display element, an illuminating device, an optical device, a display driving means, and a light deflecting device. The “image display element” is a two-dimensional array of a plurality of pixels capable of controlling light according to image information, and a liquid crystal light valve can be preferably used. The “illuminator” includes a light source and illuminates the image display element with light from the light source.

The "optical device" is for observing the image pattern displayed on the image display element. The "display driving means" forms a plurality of subfields obtained by temporally dividing the image field.

The "optical deflector" is for deflecting the optical path of the light emitted from each pixel, and the one described in claim 4 or 5 or 6 is used.

This image display device "displays an image pattern in which the display position is shifted according to the deflection state of the optical path for each subfield, so that the number of pixels of the image display element is apparently multiplied and displayed." (Claim 7).

Since this image display device uses a light deflecting device utilizing the switching of the inclination direction of the average optical axis of the chiral smectic C-phase liquid crystal layer exhibiting spontaneous polarization,
High-speed optical path deflection is possible corresponding to subfield images, and high-definition image display is apparently possible.

Further, the "fast response" of the chiral smectic C layer makes it possible to shorten the switching time of the subfield image, so that the light utilization efficiency in time is high and the temperature dependence of the "tilt angle of the optical axis" of the liquid crystal layer. Since the property is small, the temperature change in the device can be allowed to some extent, and the cooling mechanism can be simplified.

The "time of light deflection required to perform pixel shift" in the above image display device can be estimated as follows.

The image field (time: t _Field ) is temporally divided into n, and the optical path between the image display element and the optical member is deflected for every n sub-fields to shift pixel shift positions to n positions. , The time of one subfield: t _SF is represented by t _SF = t _Field / n.

Time: The light is deflected during t _SF ,
If the time is “t _shift ”, time: t
_{Since it} is not possible to display during _shift , time: t
_The light utilization efficiency is reduced by an amount corresponding to the _shift .

Light utilization efficiency: E is defined by the following equation.

E = (t _SF -t _shift ) / t _SF If the pixel shift position: n is n = 4 and the image field: t _Field is 16.7 ms, the light use efficiency: E of 90% or more is secured. Conditions for: 0.9 <{(16.7 / 4) -t _shift } / (1
The range of t _shift that satisfies 6.7 / 4) is t _shift <0.42 (ms), and it is necessary to perform light deflection in 0.42 ms. The response speed of the ferroelectric liquid crystal composed of the chiral smectic C phase can be sufficiently set to 0.42 ms or less.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

FIG. 1 shows a first embodiment of the optical deflector / optical deflector.
The form is explanatoryly shown. In FIG. 1, (a) is a top view, (b) is a front view, and (c) is a side view.

As shown in the side view of (c), the light deflection element 1 is composed of a pair of transparent substrates 2 and 3 opposed to each other with a predetermined interval, and a layered structure between these substrates 2 and 3. Retained liquid crystal layer 5 that "can form chiral smectic C phase at room temperature"
And a vertical alignment film 4 formed on the "surface on the side in contact with the liquid crystal layer 5" of at least one substrate 2.

Then, as shown in FIGS. 1 (a) and 1 (b), a direction substantially perpendicular to the layer thickness direction with respect to the liquid crystal layer 5 (see FIG.
It has one or more electrode pairs 6 (composed of electrodes 6a and 6b) arranged so that an electric field can be applied in the vertical direction in (a) and the horizontal direction in (b).

In this embodiment, the individual electrodes 6a and 6b constituting the electrode pair 6 constitute "spacer means" for separating a predetermined distance between the pair of substrates 2 and 3. . Of course, the spacer means may be a dedicated one separately from the electrode pair. The liquid crystal layer 5 is a “chiral smectic C”.
Liquid crystal material that does not form a smectic A phase at a temperature higher than the phase ”.

That is, the optical deflecting element 1 shown in FIG. 1 has a pair of transparent substrates 2 and 3 opposed to each other with a predetermined distance by a spacer means, and is held in layers between these substrates, and is kept at room temperature. A liquid crystal layer 5 capable of forming a chiral smectic C phase, a vertical alignment film 4 formed on a surface of at least one substrate 2 in contact with the liquid crystal layer 5, and a liquid crystal layer 5 substantially orthogonal to the layer thickness direction. And one or more electrode pairs 6 arranged so that an electric field can be applied in the direction in which the liquid crystal layer 5 has a chiral smectic C
It is composed of a liquid crystal material that does not form a smectic A phase at a temperature higher than the phase (claim 1).

As shown in FIG. 1C, when the electrodes 6a and 6b of the electrode pair 6 are connected to a power source 7 which is a "voltage applying means" and a voltage is applied between the electrodes 6a and 6b, the liquid crystal layer 5 is formed. To "the electric field in the direction substantially orthogonal to the layer thickness direction (" white arrow in Fig. 1 (c) ", the first electric field direction and the second electric field direction can be taken depending on the polarity of the voltage)" be able to. The average tilt direction of the optical axis of the liquid crystal layer 5 changes according to the strength and direction of the applied electric field, and the transmission path of linearly polarized light is deflected.

Therefore, the combination of the light deflection element 1 and the power source 7 shown in FIG. 1C is "electrode 6 of electrode pair 6 of light deflection element 1".
An electric field applying means 7 for applying a voltage between a and 6b to apply an electric field to the liquid crystal layer is provided, and depending on the strength and direction of the applied electric field,
This is an embodiment of an optical deflecting device (claim 4) which changes the average inclination direction of the optical axis of the liquid crystal layer 5 to deflect the transmission light path of linearly polarized light.

As shown in FIG. 1C, the optical deflector 1
When light linearly polarized in the vertical direction of the drawing is made incident on the substrate 2 from the side of the substrate 2 so as to be orthogonal to the substrate 2 and an electric field in the first electric field direction is applied, the light transmitted through the optical deflection element 1 is Figure 1
As the first emission light shown in (c), the light is shifted upward from the incident light and emitted. On the contrary, when an electric field is applied in the second electric field direction, the light transmitted through the light deflecting element 1 is emitted as the second emitted light shown in FIG. 1C, shifted downward from the incident light.

As described above, in the optical deflecting element 1 of FIG. 1, since the electrode pair provided is one pair, the deflection of light is as shown in FIG.
It is one-dimensional as shown in (b) and (c). In order to make the deflection direction two-dimensional, a second electrode pair is provided in addition to the electrode pair 6, and the direction of the electric field applied by the second electrode pair is the electric field applied by the first electrode pair. For example, it may be orthogonal to the direction.

Here, the material of the liquid crystal layer 5 will be described.
The “smectic liquid crystal” is a liquid crystal phase in which the major axis directions of liquid crystal molecules (referred to as “liquid crystal director direction”) are substantially aligned, and the liquid crystal molecules are aligned in layers while aligning the directions. In such a liquid crystal, the major axis direction of the liquid crystal molecules is
A liquid crystal phase that coincides with the normal direction of the layer (called a "layer normal direction") is called a "smectic A phase".

The liquid crystal phase of the smectic liquid crystal in which the major axis direction of the liquid crystal molecules does not coincide with the layer normal direction and is inclined with respect to the layer normal direction is called "smectic C phase". In the smectic C layer, the tilt angle at which the liquid crystal director direction is tilted with respect to the layer normal direction is called a tilt angle: θ. In the smectic A layer, the tilt angle θ is 0.

In the smectic C-phase liquid crystal, in each "layer of liquid crystal molecules", the direction of the liquid crystal director of each liquid crystal molecule is
Tilt angle: The same direction with θ. In the liquid crystal layer called "chiral smectic C phase", the liquid crystal material has asymmetric carbon in the molecular structure, and the azimuth angle of the liquid crystal director direction spirally rotates in each layer in the state where the external electric field: E does not act. It takes a "helical structure". In a chiral smectic C-phase antiferrophilic liquid crystal, the azimuth angles of the liquid crystal directors face each other in each layer.

When the liquid crystal molecule has a "permanent dipole component" in the direction perpendicular to its long axis, it is considered that spontaneous polarization: Ps exists due to the tilt angle: θ and ferroelectricity is exhibited. . Optical properties are controlled by rearranging liquid crystal molecules in a direction determined by spontaneous polarization: Ps and external electric field: E.

The light deflection element 1 will be described by taking "ferroelectric liquid crystal" as the liquid crystal layer 5 as an example, but the following description is similarly applicable to the case of antiferroelectric liquid crystal.

A liquid crystal material capable of forming a chiral smectic C phase can be generally represented by the structure shown in FIG. That is, one side of the central "skeleton part" is usually the "terminal chain of an alkyl or alkoxy group", and the other side is the "chiral part through the spacer part".

Here, "the cyclic molecules at both ends (benzene ring,
The portion sandwiched between cyclohexane rings) is the skeleton. The asymmetric skeleton often shows very different physical properties depending on whether the chiral part is attached to the left or right side. Many materials such as DOBAMBC were synthesized for the Schiff base system having a skeleton, but they are generally susceptible to hydrolysis and have a problem in stability.

Azo-based and azoxy-based materials have been synthesized, but they have problems such as photochemical deterioration and coloring. Since the biphenyl type and ester type have good chemical stability, those containing a cyclohexane ring, those having a heterocycle, and those having a ring substituent introduced are used. Generally, a polycyclic compound has a property of having a liquid crystal phase at high temperature and high viscosity. Introduction of ring substituents generally results in a lower melting point.

The spacer portion, together with the (CH ₂ ) n portion of the chiral portion, provides a skeleton portion and an asymmetric carbon space,
"-O-" or _"-OC m _{H 2m} -", "- COOC _m H
_2m- "and the like. Since “C = 0” of the ester bond contained in the skeleton and the spacer usually gives the main contribution of spontaneous polarization, the interval between “C═O” and “C *” has a great influence on the magnitude of spontaneous polarization. give.

The liquid crystal material used in the light deflecting element of the present invention "transits from the crystalline phase to the chiral smectic C phase" at a temperature of about room temperature or lower, and exhibits "chiral" at a relatively high temperature range of about 50 ° C to 100 ° C. A material that undergoes a first-order transition from a smectic C phase to a chiral nematic phase or an isotropic phase is used.

In order to set a wide "usable temperature range" of the light deflecting element, it is preferable that the temperature range of the chiral smectic C phase is wide. The "processing temperature of the substrate" at the time of injecting the liquid crystal layer is too high, which is not preferable.

Considering the operating temperature range of the light deflector, the upper limit temperature of the chiral smectic C phase is preferably between 50 ° C and 100 ° C.

When a conoscopic image of a chiral smectic C-phase liquid crystal layer in a state in which no electric field is applied is observed by a polarization microscope from the layer normal direction, a cross image is located at the center, and a uniaxial image is obtained. It can be confirmed that it has a sex optical axis.

FIG. 3 shows a model of the alignment of liquid crystal molecules in the chiral smectic C phase. The vertical direction in the figure is the layer normal direction, and the major axis direction of each liquid crystal molecule (liquid crystal director direction).
Form a tilt angle: θ and are overlapped in the layer normal direction (the figure shows “one-line overlap of liquid crystal molecules in the layer normal direction” that represents the molecular arrangement of the chiral smectic C layer). ). The liquid crystal directors of the liquid crystal molecules belonging to the same layer face the same direction. Then, in the layer normal direction, the liquid crystal director direction is “spiral” as the layers overlap.
Is turning to.

External electric field: In the state of E = 0, the orientation of the liquid crystal director in the spiral structure is "isotropic" in the direction orthogonal to the layer normal direction spatially as shown in FIG. 3 (a). When the liquid crystal director directions are averaged in the layer normal direction, the “averaged liquid crystal director direction (hereinafter referred to as“ average optical axis ”)” is in the layer normal direction as shown in the lower diagram of FIG. Turn to. In this state, the liquid crystal layer of the chiral smectic C layer is “optically isotropic” with respect to incident light parallel to the average optical axis.

When a relatively small electric field: E in the range of 0 <E <Es is applied to the "direction orthogonal to the layer normal direction" of the liquid crystal layer of the chiral smectic C layer, spontaneous polarization: electric field to Ps: E As a result, a rotation moment is generated in the liquid crystal molecules, so that the helical structure is distorted and asymmetrical as shown in FIG. 3B, and the “average optical axis” is as shown in the lower diagram of FIG. 3B. Lean in one direction. Electric field: As the intensity of E increases, the distortion increases, and the average tilt angle of the optical axis also increases. This can be confirmed by the movement of the cross image of the conoscopic image.

When the electric field strength: E is further increased and becomes equal to or higher than the threshold electric field: Es, the spiral structure disappears and becomes optically uniaxial as shown in FIG. 3 (c). The tilt angle of the optical axis in this state is equal to the tilt angle in the direction of the liquid crystal director: θ, the tilt angle: θ does not change even if the electric field is further increased, and the tilt angle of the optical axis also becomes constant.

In the optical deflecting element 1 shown in FIG. 1, the liquid crystal layer 5 made of a ferroelectric liquid crystal material of chiral smectic C phase has a "helical structure" perpendicular to the substrates 2 and 3 by the vertical alignment film 4. It forms a so-called "homeotropic orientation" in which the spiral axis is oriented.

As the orientation method for realizing the homeotropic orientation, there are known shearing stress method, magnetic field orientation method,
A temperature gradient method, a SiO oblique vapor deposition method, a photo-alignment method "or the like can be used. It can also be performed by treatment with a silane coupling agent.

One of the features of the light deflection element 1 is that the structure is simple, the manufacturing cost can be suppressed, and the influence of temperature change is small. Further, the chiral smectic C phase has extremely high-speed responsiveness as compared with the smectic A phase and nematic liquid crystal, and can switch in sub millisecond.
In particular, since the liquid crystal director direction is uniquely determined with respect to the electric field direction, control of the director direction is easier and easier to handle than in the smectic A-phase liquid crystal.

The liquid crystal layer 5 made of the chiral smectic C phase with homeotopic alignment is in homogeneous alignment (the liquid crystal director is aligned parallel to the substrate surface).
Compared with the case where the above, the operation in the liquid crystal director direction is less likely to be restricted by the substrates 2 and 3, the light deflection direction can be easily controlled by adjusting the external electric field direction, and the required electric field is relatively low. Have.

When the direction of the liquid crystal director is homogeneously aligned, the liquid crystal director strongly depends not only on the direction of the electric field but also on the surface of the substrate. Therefore, more positional accuracy is required for the installation of the light deflection element. In the case of orientation, the “setting margin” of the light deflection element 1 is large with respect to the light deflection.

In order to make full use of these features, it is not necessary to orient the spiral axis strictly "perpendicular to the substrate surface", and it may be tilted to some extent. The direction of the liquid crystal director is the substrate 2,
It suffices if it is possible to face in two or more directions without receiving the regulation force from 3.

The operation principle of the light deflecting element 1 will be described with reference to FIGS. FIG. 4 schematically shows an alignment state of liquid crystal molecules and application of an electric field by the electrodes 6a and 6b in the light deflection element 1 shown in FIG. X, Y, Z as shown
Considering the direction, the application direction of the electric field is the Y direction. The "direction of the electric field (first and second electric field directions described above)" is switched by the power source 7 in accordance with the desired deflection direction of the light.

The incident light on the light deflection element 1 is linearly polarized light, and its polarization direction is the vertical direction (Z direction) as shown by the arrow in FIG. Although not shown, electrodes 6a and 6b
It is preferable to provide an "electromagnetic shield" so that the leakage electric field from the device does not affect the peripheral devices of the light deflection element 1.

In FIG. 4, when a sufficiently large electric field (E ≧ Es described above) is applied in the Y-axis direction, as shown in FIG. 5, in the XZ cross section in the liquid crystal layer 5, the direction of the liquid crystal molecules 8 in the liquid crystal director direction. Are distributed in either the first or second alignment state depending on the direction of the electric field. Since the permanent dipole component of each liquid crystal molecule is in the direction orthogonal to the major axis direction (liquid crystal director direction), the first and second alignment states are such that the permanent dipole component is parallel to the electric field. That is,
The liquid crystal molecules 8 are “rotatable along a virtual cone shape with a tilt angle: θ”.

If the spontaneous polarization Ps of the liquid crystal is positive and the electric field E is acting in the positive direction of the Y axis (toward the front side of the paper), the rotation axis of the liquid crystal molecules 8 is in the direction perpendicular to the substrate, and thus XZ.
Within the plane. Assuming that the refractive index in the long axis direction of the liquid crystal molecules is ne and the refractive index in the short axis direction is no, linearly polarized light having a polarization direction in the Y axis direction is selected as the incident light, and when the incident light advances in the positive X axis direction, The light receives the refractive index: no as ordinary light in the liquid crystal layer 5, goes straight, goes in the “a” direction in FIG. 5A, and is not subjected to light deflection.

When linearly polarized light whose polarization direction is the Z direction is incident as in the case shown in FIG. 4, the refractive index in the incident direction is
Direction and refractive index of the liquid crystal director 8: In a refractive index ellipsoid having principal axes no and ne, it is obtained from the relationship with the direction of light passing through the center of the ellipsoid (this is a known optical fact, so here Details are omitted).

The light linearly polarized in the Z direction is converted into the light deflection element 1.
Is transmitted, the light is deflected according to the "refractive index: no, ne and the above-mentioned" average optical axis (equal to the tilt angle: θ) ", and the alignment state is the first or the second in FIG. 5B. Depending on whether or not it shifts like "b" or "b '" in FIG.

When the electric field strength E is Es or less, the tilt angle θ may be set to the “tilt angle of the optical axis” described in the lower diagram of FIG. 3B.

The tilt angle: θ (the tilt angle of the optical axis) and the optical path shift amount have the following relationship. Assuming that the layer thickness of the liquid crystal layer 5 is d, the shift amount S is expressed as follows using the above refractive indexes: no and ne and the above d.

S = [(1 / no) ² − (1 / ne) ² ] sin (2θ · d) ÷ [2 ((1 / ne) ² sin ² θ + (1 / no) ² cos ² θ)] (1) The liquid crystal layer 5 receives the light linearly polarized in the Z direction as described above.
By controlling the direction of the electric field applied to, two shift states of “b” and “b ′” in FIG. 5A are possible,
It is possible to realize a maximum shift amount of 2S by the light deflection element 1.

As an example, no = 1.55, ne = 1.
FIG. 6 shows the result of calculation of the change in the optical path shift amount S with respect to the tilt angle θ when 70 and d = 30 μm. When the tilt angle θ is 35 degrees, a deflection amount of 2S = 5 (μm) is obtained.

The above description is based on the condition that the temperature of the liquid crystal layer 5 is constant, but the characteristics of the liquid crystal layer 5 have temperature dependence. In particular, the liquid crystal material is roughly classified into two types with respect to the temperature dependence of the tilt angle: θ.

One is "a material in which the smectic A phase appears on the high temperature side of the chiral smectic C phase", and the tilt angle:
θ changes with temperature: T, and if the phase transition point is Tc, there is a relation of θ∝ (T−Tc) ^β (2). "Β" varies depending on the material, but is 0.3-
It takes a value of about 0.5. In this material system, the change of the tilt angle: θ is large particularly near the phase transition temperature, and the temperature control of the element is necessary to stabilize the optical characteristics. Conversely speaking, optical characteristics can be controlled by temperature control.

Others are "materials in which the smectic A phase does not appear on the high temperature side of the chiral smectic C phase", and the phase transition point:
A transition to a chiral nematic phase or an isotropic phase occurs at Tc or higher. This type of material has a discontinuous tilt angle: θ at the phase transition point.
Appears, but "the tilt angle in the chiral smectic C phase: θ
The temperature dependence of is relatively small. A material in which the tilt angle: θ hardly changes with temperature has also been reported.

In the light deflector of the present invention, since the above-mentioned "material in which the smectic A phase does not appear on the high temperature side of the chiral smectic C phase" is used as the liquid crystal material of the liquid crystal layer, the change of the tilt angle: θ with respect to the temperature change. Less, and therefore
There is little change in the light deflection amount (“shift amount” in the above example).

The liquid crystal material of the liquid crystal layer 5 has the structure shown in the molecular structure of FIG. 2 as "a liquid crystal material having an ester bond in at least a part of the skeleton and a carbonyl group of the ester bond being bonded to the chiral terminal side". It is preferable that at least one kind is contained (Claim 2). Further, the terminal chain thereof is an alkoxy group, and the spacer portion is “—O—” or “—OC _m H.
_{2 m} − ”is preferable.

FIG. 7 shows an example of the molecular formula of the "ferroelectric liquid crystal material". The ferroelectric liquid crystal material has a structure as shown in the upper diagram of FIG. 7, the spacer portion and the chiral portion are the same, and the skeleton portion has a structure as shown in A to D.

FIG. 7: The materials of A and B are those described in claim 2 and "the carbonyl group in the ester bond of the skeleton is bonded to the chiral terminal side". Such a material "has no smectic A phase on the high temperature side of the chiral smectic C phase and exhibits a chiral nematic phase on the high temperature side."
Tilt angle: θ has little temperature dependence.

In contrast, FIG. 7: C and D show FIG. 7:
For A and B, "only the direction of the ester bond was reversed"
However, in such a liquid crystal material, a smectic A phase appears on the high temperature side of the chiral smectic C layer, and the tilt angle: θ has a large temperature dependency.

The liquid crystal material of the liquid crystal layer 5 of the light deflecting element 1 is subjected to an external electric field in the liquid crystal layer during at least a certain period of the process of cooling from the state of the isotropic phase or the chiral nematic phase to form the chiral smectic C phase. It is preferably “applied” (claim 3).

When manufacturing the light deflection element 1, a liquid crystal material is injected into the element cell (the gap between the substrates 2 and 3) at a temperature of "isotropic phase or nematic phase" and cooled to the temperature of the chiral smectic C phase. However, the alignment state of the liquid crystal molecules near the phase transition temperature greatly affects the “uniformity of the orientation of the chiral smectic C phase”.

In the case of a liquid crystal material which forms a smectic A phase at a high temperature, liquid crystal molecules are uniformly aligned in the state of the smectic A phase in a state perpendicular to the substrate surface due to the effect of the vertical alignment treatment, as shown in FIG. 8A. It's easy to do. Further cooling from this uniform orientation state causes a tilt angle: θ below the phase transition temperature to obtain a chiral smectic C phase as shown in FIG. 8 (B) in which uniform orientation is maintained.

On the other hand, in the case of the "liquid crystal material having no smectic A phase at high temperature" used for the light deflecting element of the present invention, the liquid crystal molecules do not pass through the state of being uniformly vertically aligned with the substrate surface.

In the isotropic phase and the chiral nematic phase, FIG.
As illustrated as a chiral nematic layer in (C), "the liquid crystal molecules in the vicinity of the alignment film are vertically aligned, but the molecular arrangement is random or spiral in the central portion of the layer".

When such a "state of non-uniform alignment of liquid crystal molecules" is transferred to the chiral smectic C phase by cooling, as shown in FIG. 8D, "the orientation directions of the layers are different in the central region of the layer. In some cases, "microdomain" is formed. The existence of the minute domains causes "white turbidity of the liquid crystal layer due to light scattering and disturbance of the light deflection amount (shift amount in the above example)". It is possible to eliminate and homogenize the fine domains by applying a high-intensity lateral electric field to the liquid crystal layer in which the fine domains are generated, but it is not efficient because voltage application is required for a long time.

In the optical deflector according to the third aspect, as shown in FIG. 8, by "applying an external electric field at the phase transition to the chiral smectic C phase", the orientation uniformity of the chiral smectic C phase can be easily improved. It can be done. The external electric field may be a DC electric field or an AC electric field, and the direction and strength of the electric field can be appropriately optimized depending on the characteristics of the liquid crystal material and the characteristics of the alignment film.

The timing and time for applying the external electric field are also
It can be appropriately optimized depending on the characteristics of the liquid crystal material and the characteristics of the alignment film. As described above, according to the third aspect of the present invention, the generation of the fine domains in the liquid crystal layer 5 of the light deflection element is suppressed, the uniformity of the alignment direction in the entire liquid crystal layer can be improved, and the fine domain boundary portion can be improved. It is possible to prevent light scattering at the position and a difference in the amount of light deflection between the domains.

In the light deflecting element 1, as described above, "only the linearly polarized light in the optical path deflection direction, that is, the polarization direction parallel to the tilt direction of the liquid crystal molecules when an electric field is applied" is deflected in the optical path and is orthogonal thereto. The linearly polarized light polarized in the direction passes through the light deflection element 1 without being deflected. Therefore, FIG.
When “non-polarized light” is incident on the optical deflector as shown in (3), the emitted light contains a component that is not deflected, and the contrast with respect to the presence or absence of optical path deflection decreases.

In order to prevent such a decrease in contrast, the optical deflector according to the fifth aspect of the present invention "makes the polarization direction of the incident light on the optical deflection element 1 coincident with the average inclination direction of the optical axis of the liquid crystal layer 5. And a polarization direction control means ".

A linear polarizing plate can be used as the "polarization direction control means". The polarization direction of the linear polarizing plate is the longitudinal direction of the electrodes 6a and 6b (Z direction in FIGS. 4 and 5).
It is installed on the incident surface side of the light deflecting element 1 in parallel with.

By doing so, even if the incident light is non-polarized, the light component that is not subjected to the optical path deflecting action due to the inclination of the liquid crystal molecules is cut, so that the optical switching by the optical path deflection can be surely performed.

FIG. 9 is an explanatory view showing one embodiment of the optical deflecting device according to the present invention. Reference numerals 1A and 1B denote optical deflectors, respectively. The light deflecting elements 1A and 1B are structurally similar to the light deflecting device described with reference to FIG. 1, but for simplification of the drawing, an arrangement state of liquid crystal molecules in a liquid crystal layer, an electrode pair, Only the power supply is shown schematically. The light deflecting device 1A is the same as that shown in FIG. 1, and therefore the reference numerals of the respective parts are the same as those in FIG. In this optical deflector, electrodes 6a, 6 are provided on the liquid crystal layer of the optical deflector.
An electric field in the Y direction is applied by b.

The optical deflector 1B is structurally the optical deflector 1
Similar to A, but an electric field generated by the electrodes 6a1 and 6b1 to which a voltage is applied by the power supply 7b is applied in the Z direction in the figure.

A linear polarization plate (polarization direction control means) PL for aligning the polarization direction of the incident light in the Z direction is arranged on the incident side of the optical deflector 1A. That is, the combination of the linear polarizing plate PL and the optical deflecting device 1A constitutes the "optical deflecting device according to claim 5."

Between the optical deflecting devices 1A and 1B, "a polarization plane is 9
A ½ wavelength plate 15 is provided as “polarization plane rotating means for rotating 0 °”.

That is, in the embodiment shown in FIG. 9, the optical deflecting devices 1A and 1B according to claim 4 are arranged so that the directions of application of the electric fields in the respective optical deflecting devices are substantially orthogonal to each other, and the optical deflecting devices 1A and 1B are arranged in the light traveling direction. Light deflecting device 1A on the light incident side, which is arranged substantially in parallel
A polarization direction control means PL for matching the polarization direction of the incident light with the inclination direction of the average optical axis of the "liquid crystal layer in the light deflecting device of the light deflecting device 1A" is disposed on the incident side of. In addition, the polarization plane rotating means 15 for rotating the polarization plane by 90 degrees
It is an embodiment of an optical deflecting device (claim 6) having the above.

As the half-wave plate 15, a commercially available one for visible light can be used as it is. The light incident on the light deflector is, as shown in FIG.
It is defined as a “polarization direction in the Z-axis direction” by L, and is deflected in the vertical direction (Z-axis direction) by the optical deflecting element 1A on the front side with respect to the light traveling direction, and then by the ½ wavelength plate 15. The polarization direction is rotated by 90 ° and becomes “light in the polarization direction in the Y-axis direction” and enters the optical deflecting device 1B, and the optical deflecting element 1B
Is deflected in the left-right direction (Y-axis direction).

When such an optical deflector is used, it is possible to shift the light by two positions in the vertical direction (Z-axis direction) and two positions in the horizontal direction (Y-axis direction), and the total amount of the optical deflector is "4 positions". Light can be shifted to.

FIG. 10 shows an embodiment of the image display device according to the present invention. This image display device includes an image display element 84 in which a plurality of pixels capable of controlling light according to image information are two-dimensionally arranged, illumination devices 81, 82, 83, 87 for illuminating the image display element 84, and image display. Element 8
Optical device 8 for observing the image pattern displayed on the display 4.
5, a display driving means 88 for forming a plurality of subfields obtained by temporally dividing the image field, and an optical deflecting device 89 for deflecting the optical path of the light emitted from each pixel. This is an image display device that displays an image pattern in which the display position is displaced according to the deflection state, thereby apparently multiplying the number of pixels of the image display element 84 for display.

As the light deflection device 89, the device described in claim 4, 5 or 6 can be used, and these are used as "pixel shift elements".

The "light source" indicated by reference numeral 81 is a two-dimensional array of LED lamps, which is driven by the light source drive section 87 to emit light. The light emitted from the light source 81 is diffused by the diffusion plate 82 and illuminates the image display element 84 via the condenser lens 83. The image display element 84 is a “transmissive liquid crystal light valve”. The image display element 84 is driven by the liquid crystal drive unit 88 to display an image pattern.

The light source drive section 87 is controlled in synchronization with the drive of the liquid crystal drive section 88 as the "display drive means",
The illumination light “critically illuminates” the image display element 84.

The light, the light intensity of which is spatially modulated according to the image pattern displayed on the image display element 84, passes through the light deflecting device 89 as image light and is projected by the projection lens 85 as an "optical device for observing the image pattern". Is projected on the screen 88 to form an image pattern.

At this time, the image light is shifted by a predetermined distance in the "pixel arrangement direction in the image display element 84" by the light deflector 89. The liquid crystal drive unit 88 displays "a plurality of subfield images obtained by temporally dividing the image field", but the light deflecting means 89 deflects "an optical path for each of a plurality of subfield images", whereby the screen 86 is displayed.
The “image pattern whose display position is shifted according to the subfield image” is displayed on the upper side with a temporal shift, and the apparent number of pixels of the transmissive liquid crystal light valve 84 is multiplied and displayed.

The shift amount by the light deflecting means 89 is set to 1/2 of the pixel pitch because the image multiplication is performed twice in the pixel arrangement direction of the image display element 84. By correcting the image signal that drives the pixel display element 84 by the shift amount according to the shift amount, an apparently high-definition image can be displayed.

Since the light deflection element as in each of the above-described embodiments is used as the light deflection means 89, the utilization efficiency of light is improved, and the observer is given "brighter and higher quality light without increasing the load on the light source." Image "can be provided. Although the light deflector according to claim 4 or 5 or 6 can be used, the light transmitted through the transmissive liquid crystal light valve is in a linearly polarized state. The transmission type liquid crystal light valve also serves as the "polarization direction control means" for aligning the direction with the average tilt direction of the optical axis of the liquid crystal layer.

In such a projector device, a large amount of heat is generated from the light source, and the temperature inside the device becomes as high as about 50 degrees.
The optical element becomes even hotter due to the negligible light absorption.
Therefore, it is common to provide a cooling fan in such a device.

Further, the temperature of the inside of the projector and the optical element fluctuates greatly when the projector device is used for a long time after the power is turned on. However, if the capacity of the cooling fan is improved in order to reduce this temperature change, the cooling capacity is improved. With the improvement, the operating noise of the fan also becomes louder.

In the image display device of the present invention, since the "optical deflecting device whose optical path shift amount has a small temperature dependency" is used, the cooling mechanism in the device can be simplified or omitted.

[0119]

EXAMPLES Specific examples will be given below.

Example 1 (Optical Deflection Element / Optical Deflection Device) As a pair of transparent substrates, substrate area: 30 mm ×
A vertical alignment film (product name: JALS2021 made by Japan Synthetic Rubber) having a thickness of 0.6 μm was formed on one side surface of each of two glass substrates having a thickness of 40 mm and a thickness of 1.1 mm.
Two aluminum electrode sheets having a thickness of 30 μm, a width of 1 mm and a length of 30 mm are used as spacer means having a space width of 30 μm, and the vertical alignment films are opposed to each other with the vertical alignment film as an inner surface.
Two glass substrates were stuck together.

The aluminum electrode sheets were parallel to each other and the distance between them was 2 mm. Approximately 9 substrates on the hot plate
Volume heated by 5 degrees and surrounded by two substrates and two aluminum electrode sheets Volume: 30 μm × 2 mm × 30 m
"Ferroelectric liquid crystal that does not form a smectic A phase" was injected into the portion m by a capillary method.

The above-mentioned ferroelectric liquid crystal has the trade name: CS
2003 (manufactured by Chisso) was used.

The phase transition temperature of this liquid crystal material is as follows: crystal / chiral smectic C phase: -14 ° C., chiral smectic C
Phase / chiral nematic phase: 64 ° C, chiral nematic phase / isotropic phase: 91 ° C. Tilt angle at 25 ° C: θ
Is 30 °, birefringence: Δn is 0.18 (wavelength: 546 nm)
Is.

After the temperature of the hot plate was lowered and cooled, the hot plate was sealed with an adhesive to prepare an optical deflection element as described with reference to FIG. 24.5 μm on the incident surface side of this optical deflector
A "line / space mask pattern" having a width was provided, and illumination was performed with collimated linearly polarized light from the mask pattern side. The direction of linearly polarized light was set to be the same as the longitudinal direction of the aluminum electrode sheet.

While the temperature of the light deflection element is 25 ° C., while observing the light transmitted through the mask pattern through the “between two aluminum electrode sheets” of the light deflection element with a microscope, the pulse generator and the high speed power amplifier are When a rectangular voltage of ± 400 V was applied between the aluminum electrode sheets, the mask pattern was observed to shift in parallel. Since the mask pattern, the light deflection element, and the microscope are mechanically stationary, it was confirmed that the optical path was electrically shifted. 25 ° C
The amount of optical path shift was 5.2 μm. When the light deflection element was heated with warm air to 50 ° C., the optical path shift amount was 5.0 μm. The change amount of the optical path shift is 10% or less with respect to the temperature change of 25 to 50 ° C., and it can be said that the optical deflector has practically no temperature dependence.

The "transmittance (wavelength: 550 nm) when no electric field was applied" of this optical deflecting element was 80%. Since the distance between the electrodes of the optical deflecting element of Example 1 is as narrow as 2 mm,
Although it is difficult to use as a pixel shift element of a liquid crystal projector, it can be effectively used as an element for shifting laser light.

Comparative Example (Optical Deflection Element / Optical Deflection Device) An optical deflection element similar to that of Example 1 was prepared except that the thicknesses of the liquid crystal material and the liquid crystal layer were changed.

The liquid crystal material used here has a smectic A phase in a region higher in temperature than the chiral smectic C layer.

The liquid crystal material is trade name: CS1029 (manufactured by Chisso).

The phase transition temperatures are as follows: crystal / chiral smectic C phase: -18 ° C, chiral smectic C phase / smectic A phase: 73 ° C, smectic A phase / chiral nematic phase: 86 ° C, chiral nematic phase / isotropic phase: 95 ° C. The tilt angle θ at 25 ° C. is 25 degrees, and the birefringence Δn is 0.16 (wavelength: 546 nm). Since the tilt angle is relatively small, the thickness of the spacer means was set so that the thickness of the liquid crystal layer was 40 μm.

When the optical path shift amount was measured in the same manner as in Example 1, it was 5.2 μm at 25 ° C. and 4.0 μm at 50 ° C. The change amount of the optical path shift is about 20% with respect to the temperature change of 25 to 50 ° C., which is a practical problem. The optical deflection element as in this comparative example requires the temperature control means.

Example 2 (Optical Deflection Element / Optical Deflection Device) An element similar to Example 1 was prepared. The size of the substrate, the alignment film, the aluminum electrode sheet also serving as the spacer means, the sheet interval, and the ferroelectric liquid crystal are the same as those in the first embodiment.

In the step of injecting the ferroelectric liquid crystal into the volume surrounded by the two substrates and the two aluminum electrode sheets, it is sandwiched between the two aluminum plates so that an electric field can be applied in the thickness direction of the substrates. It was placed on a hot plate. ± 2 on two aluminum plates while the temperature drops from 70 ℃ to 60 ℃
An alternating voltage of 000 V and 60 Hz was applied.

The optical deflecting element thus manufactured had an optical path shift amount of 5.2 μm at 25 ° C. and an optical path shift amount of 5.0 μm at 50 ° C.

With respect to the temperature change of 25 to 50 ° C., the change amount of the optical path shift is within 10%, and it can be said that it is a “optical deflection element with little temperature dependence” in practical use. The transmittance (wavelength: 550 nm) when no electric field was applied was 88%, and sufficient transmittance was obtained.

By applying an external electric field (AC electric field) at the time of cooling the ferroelectric liquid crystal (without this treatment), the light deflecting element of Example 1 had a transmittance of 80% and a transmittance of 8%. Improvement has been realized. It is considered that the action of the external electric field during cooling brought the liquid crystal molecules in the chiral nematic phase closer to the vertical alignment state and improved the uniformity of the layer structure of the chiral smectic C phase.

Example 3 An “image display device (projector)” having the structure shown in FIG. 9 was prepared. Diagonal line length as an image display device: 0.
A 9-inch XGA (1024 × 768 dots) polysilicon TFT liquid crystal light valve (transmission type) was used. The pixel pitch is approximately 18 μm in both vertical and horizontal directions, and the pixel aperture ratio is approximately 50%.
Is.

A microlens array is provided on the light source side of the image display element to increase the condensing rate of the illumination light. LED of three colors of R (red) G (green) B (blue p) as a light source
A so-called field sequential system was adopted in which a light source is used to perform color display by "fast switching" of the color of light emitted to one liquid crystal light valve.

In this embodiment, the frame frequency of image display is 60 Hz, and the subfield frequency for pixel multiplication of 4 times by pixel shift is 240 Hz (60 H).
z × 4). In order to further divide one sub-frame into three colors, images corresponding to each color are switched at 720 Hz.

The LED light source of the corresponding color is turned on / off in accordance with the display timing of each color image pattern of the liquid crystal light valve.
When turned off, full color images can be observed.

In Example 1, two light deflecting elements each having an aluminum electrode sheet having a thickness of 50 μm and an electrode interval of 20 mm were formed. The longitudinal directions of the electrodes were orthogonal to each other, and they were arranged in the pixel array direction of the liquid crystal light valve. Arranged to match. A linear polarization plate was provided as a "polarization plane rotating means" between these light deflection elements.

Since the liquid crystal light valve has a function of linearly polarizing the transmitted light, the light deflector of claim 6 is constructed as shown in FIG. 9 by using this as a polarization direction control means.

A linear polarizing plate as a polarization plane rotating element was produced as follows. Substrate area: 30 mm x 40 mm,
Thickness: A thin glass substrate having a thickness of 0.15 mm was spin-coated with a polyimide-based alignment material to form an alignment film having a thickness of approximately 0.1 μm, and the glass substrate was annealed and then rubbed. Two such glass substrates were sandwiched in the peripheral portion with a spacer having a thickness of 8 μm, and bonded together so that the rubbing directions of the respective substrates were orthogonal to each other to fabricate an empty cell.

A material obtained by mixing a nematic liquid crystal having a positive dielectric anisotropy with an appropriate amount of a chiral material was injected into this empty cell under normal pressure to prepare a TN liquid crystal cell in which the orientation of liquid crystal molecules was twisted by 90 degrees. "Linear polarizing plate". It was arranged between two optical path deflecting means so that the polarization plane of the light emitted from the optical path deflecting element on the liquid crystal light valve side and the rubbing direction of the incident side surface of the linear polarizing plate coincided with each other.

A temperature sensor was attached to each light deflection element to monitor the element temperature. The rectangular wave voltage for driving each light deflecting element is ± 5 kV, the frequency is 120 Hz, the vertical and horizontal phases of the two light deflecting elements are shifted by 90 degrees, and the drive timing is set so as to shift the pixels in four directions. . The shift amount of the light deflection element under this condition was 9 μm.

By rewriting the subfield image displayed on the liquid crystal light valve at 240 Hz, "a high-definition image in which the apparent number of pixels is multiplied by 4" can be displayed in the vertical and horizontal directions. The shift switching time of each light deflecting element is approximately 0.
A sufficient light utilization efficiency was obtained in 2 milliseconds. No flicker was observed.

Immediately after the power supply of the image display device was turned on, the temperature of each light deflection element was about 25 ° C., and the shift amount was 9 μm. After about 30 minutes of use, the temperature of each light deflection element was saturated at about 50 ° C. The shift amount in this state was 8.5 μm, but the change amount of the shift amount was about 5%, and it was possible to display a high-definition and good image on the screen without any problem by visual evaluation. That is, a stable high-definition image could be obtained without providing a dedicated temperature control mechanism for the light deflection element.

[0148]

As described above, according to the present invention, a novel light deflection element / light deflection device and image display device can be realized. The optical deflector / optical deflector of the present invention has a simple structure, can be realized at low cost and compactly, has a high-speed response, can be effectively used as a pixel shift element, and is accompanied by a change in temperature. Since the change in optical characteristics is slight, there is no need for special temperature control means,
It is possible to realize stable light deflection with respect to temperature changes.

The image display device of the present invention uses the above-mentioned light deflection device as a pixel shift element to increase the apparent number of pixels while using an image display element having a small number of pixels, thereby providing a high-definition image. Can be displayed, and the temperature control means dedicated to the pixel shift element is not required.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of an optical deflecting element.

FIG. 2 is a diagram showing a basic structure of a ferroelectric liquid crystal that can be used in the light deflection element of the present invention.

FIG. 3 is a diagram for explaining a change in the direction of the “averaged optical axis” when a chiral smectic C layer and an electric field are applied to the chiral smectic C layer.

FIG. 4 is a diagram for explaining light deflection in a light deflection element.

FIG. 5 is a diagram for explaining the operation principle of the light deflection element.

FIG. 6 is a diagram showing an example of a relationship between a tilt angle and a shift amount.

FIG. 7 shows an example of a ferroelectric liquid crystal material, where A and B do not have a smectic A layer in a higher temperature region than the chiral smectic C layer, and C and D have a smectic A layer in a higher temperature region than the chiral smectic C layer. To have.

FIG. 8 is a diagram for explaining the invention described in claim 3;

FIG. 9 is a diagram for explaining one embodiment of the optical deflecting device according to claim 6;

FIG. 10 is a diagram showing a projector as one embodiment of an image display device.

[Explanation of symbols]

1 Optical deflection element A few transparent substrates 4 Vertical alignment film 5 Liquid crystal layer 6 electrode pairs

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yumi Matsuki             1-3-3 Nakamagome, Ota-ku, Tokyo, stock             Company Ricoh (72) Inventor Emura Nimura             1-3-3 Nakamagome, Ota-ku, Tokyo, stock             Company Ricoh (72) Inventor Masanori Kobayashi             1-3-3 Nakamagome, Ota-ku, Tokyo, stock             Company Ricoh (72) Inventor Yasuyuki Takiguchi             1-3-3 Nakamagome, Ota-ku, Tokyo, stock             Company Ricoh F term (reference) 2H088 EA45 GA04 HA06 HA10 JA17                       MA09                 2K002 AA07 AB04 BA06 CA14 DA14

Claims (7)

[Claims] 1. A pair of transparent substrates opposed by a spacer means at a predetermined interval, and a liquid crystal layer which is held between these substrates in a layered form and is capable of forming a chiral smectic C phase at room temperature. For the vertical alignment film formed on the surface of one of the substrates in contact with the liquid crystal layer, and for the liquid crystal layer,
And one or more electrode pairs arranged so that an electric field can be applied in a direction substantially orthogonal to the layer thickness direction, wherein the liquid crystal layer is made of a liquid crystal material that does not form a smectic A phase at a temperature higher than that of the chiral smectic C phase. An optical deflection element characterized by being provided. 2. The light deflection element according to claim 1, wherein the liquid crystal layer is bonded in the order of a terminal chain portion, a skeleton portion, a spacer portion, and a chiral terminal portion, and has an ester bond in at least a part of the skeleton portion, A light deflection element comprising at least one liquid crystal material having a molecular structure in which a carbonyl group of an ester bond is bonded to a chiral terminal side. 3. The optical deflection element according to claim 1, wherein the liquid crystal material of the liquid crystal layer is cooled from an isotropic phase or a chiral nematic phase to form a chiral smectic C phase at least for a certain period of time. An optical deflection element characterized in that an external electric field is applied. 4. The optical deflection element according to claim 1, 2 or 3, and further comprising an electric field applying means for applying a voltage between the electrodes of the electrode pair of the optical deflection element to apply an electric field to the liquid crystal layer. An optical deflecting device for deflecting a linearly polarized light transmission optical path by changing an average inclination direction of an optical axis of a liquid crystal layer according to the strength and direction of an electric field. 5. The optical deflector according to claim 4, further comprising a polarization direction control means for matching the polarization direction of the light incident on the light deflection element with the average inclination direction of the optical axis of the liquid crystal layer. Optical deflection device. 6. The two light deflecting devices according to claim 4, which are arranged substantially parallel to each other in a light advancing direction such that electric field application directions in the respective light deflecting devices are substantially orthogonal to each other, and A polarization direction control means for arranging the polarization direction of the incident light to coincide with the average inclination direction of the optical axis of the liquid crystal layer is arranged on the incident side of the light deflecting device, and the polarization plane is swung 90 degrees between both light deflecting devices. An optical deflector having a polarization plane rotating means. 7. An image display device in which a plurality of pixels capable of controlling light according to image information are two-dimensionally arranged, an illumination device for illuminating the image display device, and an image pattern displayed on the image display device is observed. Each of the above subfields, an optical device for controlling the image field, a display driving unit that forms a plurality of subfields that temporally divide the image field, and a light deflecting device that deflects the optical path of the light emitted from each pixel. By displaying the image pattern in which the display position is displaced according to the deflection state of the optical path of
An image display device, wherein the number of pixels of the image display element is apparently multiplied and displayed, and the light deflection device according to claim 4 or 5 or 6 is used.